: Is there a protocol for identifying a users's device? A user connects to my web application, I grab some sort of device ID through W3C standard protocols, The user logs in, I can then identify

@Murray155

If you're using a server-side language, you could also check for IP address. For example, in PHP:
stackoverflow.com/questions/1634782/what-is-the-most-accurate-way-to-retrieve-a-users-correct-ip-address-in-php?rq=1

... but be careful with this. Sometimes, you'll just end up with the address of a shared gateway of some sort, rather than the device itself.

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@Megan663

Web browsers do not send any identifier that is specific to a device. They send the "User-Agent" header which will generally tell you the name of the browser, version of the browser, and often the type of device.

You can set a cookie the first time that you see a visitor with a unique device ID in it. The user will send that cookie back on every subsequent page visit. Cookies sound exactly like what you want here. They are generally not shared between devices.

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